This invention relates to the art of enclosures for electronic components, circuits, and other components. It especially relates to enclosures for electronic devices, including electronic instrumentation and control circuits, as are commonly utilized in industrial and commercial environments. Of special importance is the need for space-saving enclosures that can be easily added to existing enclosures at existing facilities.
FIG. 1 illustrates some prior-art enclosures used for electronic instruments and controls. Often, instrument enclosures are designed to be installed in large openings in larger enclosures. A prior-art enclosure 11 mounts flush in a large enclosure 3. A large rectangular hole 14 must be cut in enclosure 3 to install prior-art enclosure 11. Similarly, a prior-art enclosure 12 mounts flush in large enclosure 3. A large circular hole 15 must be cut in enclosure 3 to install prior-art enclosure 12.
With flush-mounted devices, such as prior-art enclosures 11 and 12, external screws or terminal blocks are often provided on the rear side of the enclosure to terminate field wiring. The enclosure may also have provision for some kind of display or indicating lights (such as display 4), and/or pushbuttons or other devices for user input (such as pushbutton 5). Field wiring may be routed to other devices within enclosure 3, or field wiring may be routed remotely through conduits or other raceways (such as conduit 16).
Still referring to FIG. 1, prior-art enclosure 13 illustrates another typical way instrument and control enclosures are connected to larger monitoring and control systems. Prior-art enclosure 13 is typically supported on a wall or backboard with screws or similar hardware (not shown). Field wiring is typically routed into the enclosure through a conduit, such as conduit 17, to make connections to a larger system. In this case, terminal blocks are usually provided inside prior-art enclosure 13 to facilitate field-wiring connections.
While prior-art enclosures 11, 12 and 13 work well for many installations, it is often difficult to add these types of enclosures to existing facilities. Often, existing enclosures do not have space for the large openings required for prior-art enclosures 11 and 12, and there is often no wall space available for an enclosure like prior-art enclosure 13.
Even when space is not a problem, the prior art enclosures often take a lot of time to install at existing facilities. For flush-mounted enclosures, like prior-art enclosures 11 and 12, large punch tools are necessary to make the large openings, and these punch tools are often not readily available. As a result, the openings are often cut with saws. This can take a lot of time. This can also be hazardous, especially if there are live circuits in the larger enclosure.
When an enclosure similar to prior-art enclosure 13 is installed, it is necessary to provide proper support for the enclosure as well as install a conduit to make field-wiring connections to the existing larger system. This also can take a lot of time.
The prior-art enclosures are also optimized for relatively large instruments and controls. With the advancement of technology, it is often practical to reduce the size of the electronics and circuits considerably, so that much smaller enclosures are practical. The prior-art enclosures often do not scale down well.
It is therefore an object and advantage of the present invention to provide an enclosure that installs easily onto existing larger enclosures, thereby reducing the total-installed cost of instrumentation and controls. Another object and advantage is to provide an enclosure that reduces the space required for the addition of new instrumentation and controls to existing facilities.